1. Field of the Invention
The present invention relates to a system and method of performing network handover procedures for mobile communication devices, and in particular, to performing network handover procedures in between second and third generation network systems.
2. Description of the Related Art
Mobile communication has progressed substantially in the past 15 years. Communication protocols, configurations, and capabilities have advanced from first generation analog voice-only cellular systems, through second generation (2G) voice and data digital cellular systems, to third generation (3G) wide-band digital cellular systems. Currently, a third generation system called Long Term Evolution/System Architecture Evolution (LTE/SAE) is being developed, and a fourth generation wide-band network system is expected to be implemented in the future. Although most of the third generation communications devices are backward compatible with second and first generation systems, handover issues still present challenges. For example, handover of a device from a 3G LTE/SAE network, previously termed 3.9G in some corporate settings, to a third generation-second generation (3G/2G) network presents several challenges for the devices and control protocols.
Enabling seamless roaming between the various networks can only be achieved through standards and business agreements involving network operators and the vendors of wireless networking solutions. In furtherance of this objective, several alliances made up of representatives from various industry experts and executives have been established. One such alliance is the Unlicensed Mobile Alliance (UMA), which has developed technology that puts Global System for Mobile communications (GSM) traffic into IP packets, thereby enabling access to 2G and 2.5G services over unlicensed spectrum technologies, such as Wi-Fi communications networks. This allows subscribers to roam and perform handover between cellular networks and public and private unlicensed wireless networks using UMA-compliant, dual-mode devices. Another alliance is a 3rd Generation Partnership Project (3GPP)—a global corporative project in which standardization bodies coordinate Wideband Code Division Multiple Access (WCDMA) issues. 3GPP represents the most advanced wide area network solution that mobile operators can deploy.
In 2G/3G networks, a terminal is responsible of requesting quality of service (QoS) during initiation of packet data protocol (PDP) context. PDP context in a logical association between a mobile station and a public data network running across a General Packet Radio Service (GPSR) network, as defined by 3GPP. The context defines aspects such as routing, QoS, Security and Billing. QoS request is set at the application level according to the need of a particular service. As a response to the requested QoS, the terminal is given the negotiated QoS when the PDP context establishment is complete. Therefore, the terminal is aware of the actual QoS reservation in the network at the application layer. Because the terminal is heavily responsible for QoS negotiation, the capabilities of the terminal restrict the available QoS. Hence, the network can offer only the requested level of QoS, even if the requested level of QoS is not optimal for the particular service. This is a problem, which should be avoided in the LTE networks. Therefore, it is required that decisions relating to QoS in LTE networks are to be made by the network and not the terminal.
Therefore, given the progression of communication network protocols and systems and their limited geographical implementation, along with the presence of multiple network-type user terminals, there is a need for a handover method that allows for efficient and reliable handover from emerging technology network user terminals (LTE/SAE and 4G network-type user terminals) to existing network user terminals (3G/2G user terminals).